Flat panel display and method of fabricating the same

ABSTRACT

A flat panel display and method of fabricating the same are disclosed. The flat panel display includes a first substrate having a pixel region; a light-emitting element located on the pixel region; a second substrate located opposite the first substrate; and a sealant located between the first and second substrates to cover the light-emitting element. At least one of the first and second substrates includes a groove formed around at least a portion of the circumference surrounding the pixel region. When the first and second substrates are pressed together with the sealant between them, the sealant spreads, covering the light-emitting element, and at least partially filling the groove.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.11/100,137, filed Apr. 5, 2005, which claims priority to and the benefitof Korean Patent Application No. 2004-23893, filed Apr. 7, 2004, thedisclosure of which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a flat panel display and method offabricating the same and, more particularly, to a flat panel display andmethod of fabricating the same including a sealant covering alight-emitting element.

BACKGROUND OF THE INVENTION

An electroluminescence display, being a type of flat panel display, isan emissive display and has advantages of a wide viewing angle, goodcontrast and fast response speed. For these reasons, electroluminescencedisplays have attracted attention as the next generation of displays. Anelectroluminescence display includes a light-emitting element having ananode, a cathode, and an emission layer interposed between the anode andthe cathode, and is classified as either an inorganicelectroluminescence display or an organic electroluminescence displayaccording to the type of the emission layer.

In the organic electroluminescence display, the light-emitting elementis susceptible to being damaged by exterior moisture. Therefore, inorder to protect the light-emitting element from exterior moisture,various techniques for encapsulating the light-emitting element using anencapsulating substrate have been developed. One of the encapsulatingtechnologies is a method of applying a sealant on a circumference of aregion in which the light-emitting element is formed, and bonding theencapsulating substrate using the sealant as a bonding medium. However,since the sealant has a defined width, it is difficult to fully preventmoisture or oxygen from the exterior environment from penetrating thesealant. In order to improve this, a technique has been developed bywhich sealant is applied to the entire region in which thelight-emitting element is formed.

FIGS. 1 a and 1 b are cross-sectional views illustrating conventionalmethods of encapsulating an organic electroluminescence display.

Referring to FIG. 1A, a mother substrate 10 including a plurality ofcell regions 10 a and scribing lanes 10 b defined by the cell regions 10a is provided. Each of the cell regions 10 a includes a pixel region 10aa and a pad region (not shown) located in a predetermined region of theperiphery of the pixel region 10 aa. Then, light-emitting elements 25are formed in the pixel regions 10 aa, respectively.

Meanwhile, an encapsulating substrate 50 is provided, and a sealant 40is applied on a predetermined region of the encapsulating substrate 50.The region where the sealant 40 is applied corresponds to the pixelregion 10 aa of the mother substrate 10. Then, the encapsulatingsubstrate 50 is disposed in a way such that the surface of theencapsulating substrate 50 to which the sealant has been applied facesthe mother substrate 10.

Referring to FIG. 1B, the encapsulating substrate 50 and the mothersubstrate 10 are bonded together by applying pressure. At this time, thesealant 40 may be squeezed out up to the circumference of the pixelregion 10 aa, as defined by the scribing lane 10 b and the pad region bythe pressure.

Subsequently, the scribing lane 10 b is scribed to separate therespective cells 10 a, thereby manufacturing the organicelectroluminescence display. In the scribing process, the sealant 40squeezed out to the scribing lane 10 b between adjacent cells 10 a maycause adjacent cells to attach to each other, thereby causing aseparation defect, i.e., a scribing defect between cells 10 a adjacentto each other. In addition, an additional process step is required inorder to remove the sealant 40 squeezed out to the pad region, i.e., thesealant 40 incorrectly formed on the pad region.

In order to solve the problem, Korean Patent Application No. 2002-28714discloses “Method of encapsulating OLED and OLED panel using the same.”According to the Korean Patent, the method of encapsulating OLEDincludes forming a partition wall by applying a first sealant to aregion of an encapsulating substrate, wherein the region face a regionenclosing a selected OLED of a plurality of OLEDs formed on a substrate,filling a second sealant in an opened space formed by the first sealant,bonding the encapsulating substrate and the substrate using the firstand second sealants as mediums by applying pressure, and curing thefirst and second sealants to encapsulate the OLED. However, although thefirst sealant is formed of a high viscosity material, the method has aproblem in that the first sealant may be squeezed out up to an outerperiphery by the pressure for bonding the substrate and theencapsulating substrate. Therefore, the aforementioned problems maystill occur.

SUMMARY OF THE INVENTION

The present invention provides a method of encapsulating a flat paneldisplay and flat panel display manufactured thereby, which is capable ofreadily controlling the region in which the sealant is formed.

In an exemplary embodiment of the present invention, a flat paneldisplay includes: a first substrate having a pixel region; alight-emitting element located on the pixel region; a second substrateopposite to the first substrate; and a sealant located between the firstand second substrates to cover the light-emitting element. At least onesubstrate of the first and second substrates is provided with a grooveformed along a circumference of the sealant for containing excesssealant.

The second substrate may be a glass substrate or a plastic substrate.

The groove may be formed along an entire circumference of the sealant.In one embodiment of the invention, the groove has a depth of betweenabout 20 and about 500 μm. In another embodiment of the invention, thegroove has a width of between about 0.1 and about 5 mm.

The light-emitting element may include a first electrode, an emissionlayer and a second electrode, which are sequentially stacked on thesubstrate. The second electrode may be a transparent electrode. Inaddition, the sealant may be a transparent sealant. Furthermore, thesealant may be a thermosetting sealant or a UV light curing sealant.

In one embodiment of the invention, the flat panel display also includesan optional moisture-absorbing layer located between the sealant and thesecond substrate. The moisture-absorbing layer may be a layer formedusing an alkaline earth metal oxide.

In another exemplary embodiment according to the present invention, amethod of fabricating a flat panel display includes: providing a firstsubstrate and a second substrate each having a pixel region; forming alight-emitting element on the pixel region of the first substrate;forming a first groove surrounding the pixel region of the firstsubstrate and/or a second groove surrounding the pixel region of thesecond substrate; applying a sealant in a region defined by the grooveof the second substrate; disposing the second substrate to direct theapplied sealant toward the first substrate; and bonding the first andsecond substrates together by applying pressure.

Forming the groove may be performed using methods such as etching,sandblasting or molding.

In one embodiment, the method further includes, after bonding the firstand second substrates, irradiating heat or UV light to the sealantthrough the first and/or second substrates in order to cure the sealant.Furthermore, the method may further include, after forming thelight-emitting element, forming a passivation layer covering thelight-emitting element on the first substrate. Meanwhile, the method mayfurther include, before applying the sealant on the second substrate,forming a moisture-absorbing layer on the second substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will be describedin reference to certain exemplary embodiments thereof with reference tothe attached drawings in which:

FIGS. 1A and 1B are cross-sectional views illustrating a conventionalmethod of encapsulating an organic electroluminescence display; and

FIGS. 2A to 2C are cross-sectional views illustrating a method offabricating a flat panel display in accordance with an embodiment of thepresent invention.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments are described below in order to explain thepresent invention by referring to the figures.

FIGS. 2A to 2C are cross-sectional views illustrating a method offabricating a flat panel display in accordance with an embodiment of thepresent invention.

Referring to FIG. 2A, a first substrate 100 having cell regions 100 cand scribing lanes 100 s located between the cell regions 100 c isprovided. Each of the cell regions 100 c includes a pixel region 100 caand a pad region (not shown) located at a periphery of the pixel region100 ca. The first substrate 100 may be a glass, quartz or plasticsubstrate.

At least one light-emitting element E is made on the respective pixelregions 100 ca. The light-emitting element E is made by forming a firstelectrode 120 on the first substrate 100, forming an emission layer 125on the first electrode 120, and then forming a second electrode 130 onthe emission layer 125. The emission layer 125 is preferably formed ofan organic light-emitting material. In this case, before forming theemission layer 125, a first charge injection layer and/or a first chargetransport layer may be formed on the first electrode 120. Furthermore,before forming the second electrode 130, a second charge injection layerand/or a second charge transport layer may be formed on the emissionlayer 125. Either or both of the first and second electrodes 120 and 130may be formed of a transparent electrode. Optionally, one of the firstand second electrodes is formed of a reflective electrode.

Preferably, a passivation layer 140 covering the light-emitting elementE is formed on the light-emitting element E. The passivation layer 140may protect the light-emitting element E from physical or chemicalstimulation of the exterior, and may be formed of an organic layer, aninorganic layer, or a composite layer thereof.

While forming the first electrode 120 and/or the second electrode 130, apad electrode is formed on the pad region. The pad electrode is aterminal to be electrically connected to FPC (Flexible Printed Circuitfilm), COG (Chip On Glass) or COF (Chip On Film).

Subsequently, a second substrate 150 is provided. The second substrate150 may be a glass or plastic substrate. Grooves G are formed onpredetermined regions of the first and second substrates 100, 150. Itshould be noted that while grooves G are shown on both the first andsecond substrates 100, 150, in other embodiments, a groove G may beformed on just a predetermined region of the first substrate 100, or onjust a predetermined region of the second substrate 150. When the grooveG is formed on the first substrate 100, the groove G is formed in aregion surrounding the pixel region 100 ca. Similarly, when the groove Gis formed on the second substrate 150, the groove G is formed on aregion corresponding to the region surrounding the pixel region 100 ca.Preferably, the groove G is formed to fully surround the pixel region100 ca. The groove G may be formed using an etching, sandblasting, ormolding method, but its formation is not limited to such methods.Furthermore, in one embodiment, the groove G is preferably formed tohave a depth D between about 20 and about 500 μm. In another embodiment,the groove G is preferably formed to have a width W between about 0.1and about 5 mm.

A sealant 165 is applied to a region of the second substrate thatcorresponds to the pixel region 100 ca of the first substrate 100. Forthis embodiment, the region is also defined by the groove G of thesecond substrate 150. Examples of suitable sealants 165 includethermosetting or UV light curing types of sealants. In one embodiment,the sealant 165 is a transparent sealant. Therefore, light emitted fromthe light-emitting element may be emitted to the exterior through thesecond substrate 150. That is, a top emission flat panel display may beimplemented. However, not limited thereto, it is also possible toimplement a bottom emission type emitting light through the firstsubstrate 100 or a double sided emission type emitting light throughboth the first and second substrates 100 and 150.

Before applying the sealant 165 on the second substrate 150, in oneembodiment, a moisture-absorbing layer 161 may be formed on the secondsubstrate 150. In yet another embodiment, the sealant 165 may contain amoisture-absorbing material. According to this embodiment, themoisture-absorbing material may be contained in the sealant 165 in adistributed manner, and the sealant 165 may function as a binder for themoisture-absorbing material.

Examples of suitable materials for the moisture-absorbing layer 161include alkaline earth metal oxides. Examples of alkaline earth metaloxides include calcium oxide and barium oxide.

Referring to FIG. 2B, the second substrate 150, on which the sealant 165is applied, is disposed to direct the applied sealant 165 toward thefirst substrate 100 when the first and second substrates 100 and 150 arepressed together, thereby bonding the first and second substrates 100and 150 using the sealant 165 as a medium. At this time, thelight-emitting element E of the pixel region 100 ca is buried into thesealant 165. That is, the sealant 165 covers the light-emitting elementE. At the same time, the sealant 165 is squeezed out of the pixel region100 ca by the pressure. However, the squeezed sealant 165 meets thegroove G to stop its outward movement as the excess sealant fills thegroove G. Therefore, it is possible to prevent the sealant 165 fromextending past the scribing lane 100 s or the pad region. In otherwords, the flow of the sealant 165 may be readily controlled by thegroove G. Therefore, the need for removing sealant incorrectly formed onthe pad region may be omitted, and it is possible to prevent scribingdefects from occurring due to the sealant incorrectly forming on thescribing lane 100 s.

According to one embodiment, the groove G is located along at least aportion of a circumference of the sealant 165. Preferably, the groove Gis located along the entire circumference of the sealant 165. Formingthe groove G along the entire circumference of the sealant 165 may beimplemented by forming the groove G to entirely surround the pixelregion 100 ca.

In one embodiment, the pressing of the second and first substrates 150and 100 is performed in vacuum or inert gas atmosphere. This helps toprevent oxygen or moisture from penetrating into the light-emittingelement E.

Subsequently, the sealant 165 may be cured such as by irradiating heator UV light to the first and second substrates 100 and 150.

Referring to FIG. 2C, the cells are separated by applying physical forceto the scribing lanes 100 s of the first and second substrates 100 and150. Each of the separated cells is defined as one flat panel display.

As can be seen from the foregoing, in a method of fabricating a flatpanel display, the flow of sealant during the sealing process is readilycontrolled using one or more grooves formed on a predetermined region orregions of one or both of the first and second substrates to containexcess sealant.

Although the present invention has been described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that a variety of modifications and variations may bemade to the present invention without departing from the spirit or scopeof the present invention defined in the appended claims, and theirequivalents.

1. A method of fabricating a flat panel display, comprising: providing afirst substrate having a pixel region that defines a pixel regioncircumference; forming a light-emitting element on the pixel region ofthe first substrate; providing a second substrate; forming a groove onat least a portion of at least one of the first and second substrates,the groove corresponding to the pixel region circumference of the firstsubstrate; applying a sealant to one of the first and second substratescorresponding to the pixel region circumference; pressing the first andsecond substrates together to thereby spread the sealant between thefirst and second substrates and outwardly toward the groove.
 2. Themethod according to claim 1, wherein forming the groove is performed bya method selected from etching, sandblasting and molding.
 3. The methodaccording to claim 1 further comprising curing the sealant with heat orUV light applied through at least one of the first and secondsubstrates.
 4. The method according to claim 1, further comprisingforming a passivation layer covering the light-emitting element on thefirst substrate.
 5. The method according to claim 1, further comprisingforming a moisture-absorbing layer on the second substrate.
 6. Themethod according to claim 1, wherein the sealant contains amoisture-absorbing material.